1. Field of the Invention
The present invention relates generally to large metallic vessel construction and modification, and, more specifically, to an anchor for use interior of a vessel and a method for installing stainless steel components in vessels without releasing hexavalent chromium in the vessels.
2. Description of the Related Art
In February 2006, the U.S. Department of Labor's Occupational Safety and Health Administration (O.S.H.A.) published its new standard for occupational exposure to hexavalent chromium. Hexavalent chromium, also known as chromium (VI) or Cr (VI), is a natural metal used in a wide variety of industrial activities, including the manufacture of stainless steel, welding, painting and pigment application, electroplating, and other surface coating processes. O.S.H.A. determined that the new standard is necessary to reduce significant health risks posed by occupational exposure to chromium (VI).
The standard covers the general industry, construction, and shipyards sectors and will protect workers against exposure to hexavalent chromium, while providing employers with adequate time to transition to the new requirements.
Large metallic vessels, such as high temperature chemical processing tanks, are often constructed with a large number of spaced metallic anchors attached to their interior surfaces. These anchors are typically used for anchoring refractory materials to the interior walls of the vessel for protecting the vessel from damage from the high temperature chemical processes occurring therein. The anchors are typically made of stainless steel. The vessel walls are typically constructed of carbon steel.
According to known methods of the prior art, the anchors are installed in the vessels by ironworkers by spot or stud welding. The ironworkers must generally enter the vessels to accomplish the welding work. The process of welding the grades of steel of which the anchors are generally made to carbon steel generates airborne hexavalent chromium. Hexavalent chromium has been determined to create a health hazard when released into a confined space so that it contaminates the breathing air. To avoid this health hazard, workers have heretofore generally worn HEPA-type half-mask filters over their mouth and nose.
The new O.S.H.A. standards require greater worker protection than is provided by the half-mask filters previously used. The new standards require that workers exposed to hexavalent chromium wear full-mask respirators having oxygen provided to the workers from an external source. The standards also require that a worker exposed to hexavalent chromium inside a closed vessel be harnessed and tethered to a worker outside the vessel, so that he can be quickly removed from the vessel in the event of loss of consciousness. The new O.S.H.A. standards are much more burdensome on both employers and their ironworkers than the prior standards were. The full mask respirators and oxygen supply and related equipment are quite expensive. In addition, ironworkers generally find it more cumbersome and difficult to work while wearing full-mask respirators attached to oxygen supply hoses.
A need therefore exists for a method for installing anchors or other components comprising stainless steel in metallic vessels without requiring the ironworkers to comply with the new, more stringent O.S.H.A. standards or an anchor that provides the benefits of stainless steel without the corresponding problem associated with welding the stainless steel to the interior of a carbon steel vessel. Preferably, the method will permit the components to be installed without releasing hexavalent chromium into the vessels.